Xanthines

Xanthine ( /ˈzænθiːn/ or /ˈzænθaɪn/; archaically xanthic acid) (3,7-dihydro-purine-2,6-dione), is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine.